DETROIT — State health officials have issued a host of new warnings in their Eat Safe Fish Guides, manuals that help Michigan residents eat fish that contain fewer pollutants.

After reviewing the latest research, they realized a common pollutant — PFOS, one of the man-made "forever chemicals" known collectively as PFAS — is more toxic than they knew.

The realization led to hundreds of strengthened and additional warnings in Michigan's fish consumption guidebooks, affecting multiple fish species and waterbodies.

Studies on humans and lab animals both have shown that low levels of PFOS can harm immune systems, said Lynn Sutfin, spokesperson for the Michigan Department of Health and Human Services.

In response, the department reduced the concentration of exposure they consider protective by nearly 80%, from 14 nanograms per kilogram to just 2.89 nanograms per kilogram.

Michigan's 2025 Eat Safe Fish Guide is littered with examples of PFOS warnings. Sutfin said 305 existing warnings became stricter and 277 new ones were created by the tighter limits on PFOS.

For example, health officials suggest eating no more than four servings of bluegill from Oakland County's Long Lake per month because of PFOS levels, and no more than two servings of yellow perch from the Belle River in St. Clair County.

"I personally don't eat a lot of fish for that reason," said Brittanie Dabney, a Ph.D. candidate at Wayne State University who studies PFAS and microplastics pollution. "I tend to stay away from fish or follow the advisories."

Dabney said the state needs to make sure anglers are told about fish consumption warnings. Some people rely on fish for food, so it's important they know how to choose fish and fishing spots safely, she said.

PFOS and other contaminants are often stored in sediment, Dabney said. That's how they get into the food chain. She recommended people avoid eating catfish and other fish that spend a lot of time in sediment.

She also recommended against fishing in polluted areas.

"Trying as best as possible to stay away from industrial areas, or downstream of industrial areas," Dabney said. "Being mindful of how you prepare the fish, where you're getting the fish from and then also being vigilant about what's happening in your community ... If there's a polluter in the area, to report them."

There are methods of preparing fish to reduce the contaminants in a meal, the state health department said. Trimming away fat and organs or grilling or broiling fish can reduce the amount of some chemicals that are stored in fat.

But that doesn't work for PFOS or mercury, since those contaminants are stored in the filet, according to Michigan's fish consumption guide.

The recommendations in Michigan's Eat Safe Fish guide are based on the levels of chemicals state scientists find in fish filets. The recommendations aren't laws, just advice for avoiding dangerous levels of pollutants in locally caught fish.

"There are many health benefits to eating fish and the Eat Safe Fish Guides provide consumption recommendations based on the levels of certain chemicals found in fish in waterbodies across the state," said Dr. Natasha Bagdasarian, Michigan's chief medical executive. "Michigan families can use these guidelines to help make healthy choices about the fish they eat."

The Great Lakes PFAS Action Network advocacy group applauded Michigan's new fish consumption recommendations that tighten the amount of PFOS considered safe over the long term.

"This is a major win for public health and a long-overdue acknowledgment of the science on PFAS," said Tony Spaniola, action network co-chair. "These new guidelines will help protect people across Michigan — especially in frontline communities that rely on fish as a food source."

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